When working with concrete, contractors may encounter a few different problems. The following issues can sometimes occur when pouring concrete slabs. While some aspects of working with concrete slabs have changed over the years, many issues have not. Here are three common problems that come with pouring concrete slabs, and their possible solutions.
1) Excessive Bleeding
Bleeding occurs when the heavy ingredients in concrete (aggregate and sand) settle and push the extra water to the top of the slab.Concrete that bleeds for too long or too fast can cause problems like sand streaks in walls; weak horizontal construction joints; rock jams in pump lines; etc. Finishing a concrete slab before bleed water has evaporated can cause cracking, dusting, scaling and low-wear resistance.
Excessive bleeding can be avoided by not adding too much water to the concrete; placing concrete at the lowest possible slump (if you need a higher slump to speed placement, consider using a superplasticizer); using a more finely ground cement; adding more cement to the mix; blending in a fine blow sand or fly ash.
2) Curling
Curling happens when a slab rises up at corners and edges – or sometimes at a mid-panel crack. It happens when the top section of a concrete slab dries or cools faster than the bottom section. Curled concrete slabs can be fixed, but it is expensive.
Grinding can level out the edges, and grout can be used to restore support to the slab. The best way to avoid curling is to control it before it happens. There are a number of material choices, construction practices and design decisions that will help prevent curling from happening in the first place.
3) Thin slab
All concrete slabs have varied thicknesses – some parts of the slab are thicker than others. When it comes to thin slabs, the thinnest sections may be too thin to retain their strength and may be prone to crumbling. In such cases, the contractor needs to decide how thin is too thin.
They must decide whether to make the slabs thicker for the sake of giving additional strength and durability to the concrete slab. Contractors should also pour thin slabs very carefully and ensure that the depth of concrete is even throughout the slab.
These are three of the most common problems that can arise when working with concrete slabs. They are easy to fix; taking care while pouring the concrete and being precise with measurements is the best way to avoid these problems in the first place.
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